Boklage C E
Genetics Program, East Carolina University School of Medicine, Greenville, North Carolina.
Acta Genet Med Gemellol (Roma). 1987;36(3):275-88. doi: 10.1017/s0001566000006036.
For epidemiological purposes, it is customary to assume that same-sex (SS) dizygotic (DZ) twin pairs are approximately equal in number to unlike-sex (OS)-DZs, the remainder of the SS pairs being monozygotic (MZ). It is also customary to consider OS-DZs to be epidemiologically representative of all DZs, which can only mean that difference in frequency of any trait between OS and SS twins is due to the MZ fraction of the SS twins. Since this is assumed as a premise, there is little value in its usual appearance as the result. The basic tenet of twin biology, that most twin excess anomalies are due to MZs, is a myth self-perpetuated by a methodological tautology, and is false, at least for mortality. In a consecutively ascertained and prospectively studied sample of 616 twin pairs, over 80% diagnosed for zygosity, it can be shown that the standard assumption mentioned above have given impossible answers. The most probable possible answer is that mortality does not differ greatly with zygosity overall, but that SSDZ mortality is much higher than that of OS twins, and probably even higher than that of MZs. Race differences in the probable answers further suggest that standard assumptions of the Weinberg method may have consistently provided false explanations for race differences in the OS fraction of twin pairs.
出于流行病学目的，通常假定同性（SS）双卵（DZ）双胞胎对的数量与异性（OS）-DZ双胞胎对大致相等，其余的SS对为单卵（MZ）双胞胎。通常还认为OS-DZ双胞胎在流行病学上代表所有DZ双胞胎，这只能意味着OS和SS双胞胎之间任何性状频率的差异是由于SS双胞胎中的MZ部分造成的。由于这是作为一个前提假设的，所以它通常作为结果出现并没有什么价值。双胞胎生物学的基本信条，即大多数双胞胎的额外异常是由MZ双胞胎引起的，是一个因方法上的同义反复而自我延续的神话，并且是错误的，至少在死亡率方面是错误的。在一个连续确定并前瞻性研究的616对双胞胎样本中，超过80%的双胞胎对已诊断出合子性，可以证明上述标准假设给出了不可能的答案。最有可能的答案是，总体而言，死亡率在合子性方面差异不大，但SSDZ双胞胎的死亡率远高于OS双胞胎，甚至可能高于MZ双胞胎。可能答案中的种族差异进一步表明，温伯格方法的标准假设可能一直为双胞胎对中OS比例的种族差异提供了错误的解释。
